1. Field of the Invention
The present invention relates generally to an apparatus for and a method of controlling a motion mechanism incorporating therein an actuator for regulatively moving a movable member, and more particularly, to a technology for detecting a signal produced by a position sensor at a reference position of the movable member in the motion mechanism during the movement of the movable member by the actuator.
2. Description of the Related Art
Japanese Unexamined Patent Publication No. 2005-188286 discloses a variable valve mechanism which rotates a control shaft by means of an actuator, to variably and continuously control a lift amount of an engine valve and an operating angle thereof.
Further, the above Publication discloses that the actuator is controlled so that the valve lift amount reaches a minimum value during the fuel cut-off of the engine, and when it is determined that the valve lift amount reaches the minimum value, an output of a sensor that produces a signal indicating an angular position of the control shaft is detected and a correlation between the output of the sensor and the angular position of the control shaft is adjusted for correction.
In the case where the valve lift amount is set to take the minimum value, the rotation of the control shaft is restricted to be stopped by an appropriate stopper member. However, a torque of the actuator continues to be applied to the control shaft.
Herein, in the case where the sensor detecting the angular position of the control shaft is comprised of a magnet mounted on an end portion of the control shaft and electromagnetic conversion means fixedly arranged at a position facing the magnet, if the torque of the actuator continues to be applied to the control shaft, a mounting portion of the magnet is deflected while causing a variation of the sensor output.
Consequently, there occurs such a problem that the sensor output for a case when the valve lift amount is made to be the minimum value cannot be detected with high precision.